Predetermined torque release wrench



Dec. 15, 1953 O. B. HARMES PREDETERMINED TORQUE RELEASE WRENCH FiledApril 9, 1951 Patented Dec. 15, 1953 PREDETERMINED TORQUE RELEASE WRENCHOren B. Harmes, Algona, Iowa, assignor to Livingston Tool 00., Algcna,Iowa, a partnership Application April 9, 1951, SerialNo. 219,903

7 Claims.

This invention relates to torque wrenches. More particularly it relatesto a torque wrench constructed to automatically release when the torqueexerted thereon exceeds a predetermined torque so as to positivelyprevent the element being tightened by the wrench from being damaged byan excessive torque.

In various mechanical assembling operations and in various otheroperations such as in rolling or expanding tubing into ferrules, it isnecessary to be able to rotate elements such as bolts, nuts, expandersetc. until and only until the resistance offered thereto reaches apredetermined .force and requires a torque in excess thereof to overcomethe same. It is imperative that the torque applied to such elementsnever exceed a predetermined amount in order to insure that irrepairabledamage is not done. My invention is directed toward providing a wrenchwhich will positively prevent such damage.

It is a general object of my invention to provide a novel and improvedtorque wrench constructed to positively prevent tightening of an elementtherewith beyond a predetermined torque.

A more specific object is to provide a novel and improved torque wrenchwhich will automatically release its element engaging member when thetorque applied thereto exceeds a predetermined amount.

Another obiect is to provide an automatically releasing torque wrenchwhich is reversible in nature to permit its use for rotating an elementin either direction and for releasing such element from said turningaction when a predetermined torque is exceeded.

Another object is to provide an automatically releasing torque wrenchcapable of ready adjustment to cause the same to release the element tobe turned from turning action at various predetermined torques.

These and other objects and advantages of my invention will be moreapparent from the following description made in connection with theaccompanying drawings, wherein like reference characters refer tosimilar parts throughout the several views and in which:

Fig. 1 is a longitudinal sectional View of one embodiment of myinvention.

Fig. 2 is a side elevational view of the same with the head member shownin longitudinal section taken in a plane at right angles to the planeshown in Fig. '1.

Fig. 3 is a top plan view of the head member with the top plate intactand of the interior shank portion of the handle.

Fig. 4 is a cross sectional view of the handle taken along line 4-4 inFig. 1.

One embodiment of my invention may include as shown in Figs. 1-4 aninteriorly tapped handie member indicated generally as H and havingrigidly secured thereto at its outer end a head member 6. The headmember 5 has a hollowed out (portion 7 formed therein, this hollowedarea being somewhat elongated but approximately circular at its largestend portion 8. The shape of this hollowed out area i is best shown inFig. 1. An opening ta is formed in the bottom wall of the hollowed outhead mem er so that a passage extends transversely through the headmember 6. This is best shown in Fig. 2. Mounted for rotation in thecircular portion 8 is a rotatable body or socket 9. This socket *3 hasan opening it extending therethrough of the proper size and shape toengage the element desired to be turned by the wrench. The socket it hasa central circumferential rib H which provides a shoulder #32 tocooperate with a ring it to hold the socket from sliding outwardly fromthe head member ii. A plate i l is secured to the other side or" thehead member by cap screws it, this plate it having an opening it thereinor" sufiicient size to permit the outer edge portions of the socket toextend outwardly therethrough. Formed in the outer circumferentialsurface of the central rib H of the socket 9 is a recess or groove il'which extends parallel to the axis of rotation of the socket. Absentengaging element the socket 9 is free to rotate in the enlarged portion8 or" the head member but is confined to that portion.

The handle H is comprised 01' a shank it which as shown in Fig. l isformed integrally with the head member 6. This shank it has alongitudinally extending bore ill which communicates with the hollowedout portion l of the head 6 and which extends throughout its entirelength. The medial portion of the shank i3 is externally threaded as at23 while the rearward or inward portion is reduced as at ii. The extremeinner end of the shank I3 is provided with a pair of inwardly extendingshoulders 22 which are disposed opposite each other as best shown inFigs. 1 and 4. The shank it is graduated as at along the circumferentialsurface of its outer end portion.

The other section of the handle H is internally threaded as at Tel tocooperate with the external threads 28 of the shank 8 as best shown inFig. 1. This section has an interior bore extending inwardly from itsouter end and of suificient diameter to accommodate the shank it.

The bore is of sufficient length to also accommodate a relatively strongspring 25 which is maintained at its inner end in central position withrespect to the bore by a plug 26 having a reduced head 2'? adapted to beinserted within the spring. Also formed in this section of the handle isreading hole 28 and an internally threaded aperture 29 adapted toreceive a set screw 26.

Mounted for limiting sliding movement within the shank it of the handleH is a rod 3| as best shown in Fig. 1. The inner end of this rod isexternally threaded as at 32 to threadedly receive the nut 33 ofexternal diameter equal to the spacing between the opposed shoulders 22.As best shown in Fig. 1 this rod 3i is of suificient length so that itsinner end extends inwardly beyond the shank i8 and the nut to bereceived in the outer end of the spring 25 and is of sufficient lengthso that its outer end 3% extends into the hollowed out area 7 of thehead member 6.

The outer end of the rod 3! is flattened and reduced as at 35 to receivethe inwardly extending bracket arms of a toggle member indicatedgenerally as T. The bracket arms (iii are spaced from each other toaccommodate the flattened portions 35 therebetween and have aperturesformed therein to accommodate a pivot pin 3: which extends through eachof the arms 38 and the flattened portion 35. This pivot pin 37 isarranged to extend transversely with respect to the rod SI and on anaxis substantially parallel to the axis of rotation of the socket member9.

The toggle member T is provided with an out wardly extendingcircumferential shoulder 38 and is further provided at its outer endportions with a cylindrically shaped key 39. This key 39 extendstransversely with respect to the rod ti and substantially parallel tothe pivot pin 3'3. The key 39 is so shaped as to complement and snuglyset into the groove ll formed in the socket member 9. A relatively weakspring 46 is carried by the outer end 35. of the rod 3! and by the innerend of the toggle member T. This spring abuts against the shoulder 33and against the wall of the head member 6 which defines the hollowedarea The walls of the hollowed area i are sufficiently spaced from thetoggle member T so that the latter may swing sufficiently far to eitherside of the longitudinal center of the rod 3! to cause the key as tobecome completely disengaged from the socket member 9.

When the wrench is assembled for use, the respective parts are inrelation to each other as best shown in Fig. 1. By referring to Fig. 1it can be seen that the section of the handle which receives the shankportion I8 is threaded onto the shank sumciently far to exert thedesired compression on the spring 25. When this has been done, the setscrew 36 is tightened and thereafter the socket 9 will be prevented fromturning by the toggle T until a sufficient torque has been exertedthereon to cause the toggle T to cam over, thereby compressing thespring 25. It can be readily seen that in normal position the toggle Textends diagonally with respect to the rod 3! and is constantly urgedtoward engaging relation with respect to the socket 9. At the same timethe spring 25 constantly urges outwardly against the nut 33 to tend toprevent the rod 35 from being moved inwardly.

In operation the wrench is arranged so that the socket 9 will engage thebolt, nut, pin or other element desired to be rotated. The necessarytorque is then applied to the handle H to rotate the element. So long asthe resistance offered by the element being turned does not exceed apredetermined torque arrived at by the amount of compression placed uponthe spring 25, the wrench will continue to tighten the element. However.when this predetermined torque is exceeded the toggle '1 will cam overto the opposite side and in so doing will compel the rod (ii to moveinwardly, overcoming the outward thrust of the spring 25. By cammingover, the toggle T automatically, for all practical purposes, releasesthe socket 9 since a much lower torque will be required to cause the key39 to slide out of the groove ll, thus permitting the socket 9 to rotatefreely relatively to the handle I-i. Thus it can be seen that it becomesimpossible with this wrench regardless of carelessness or abuse in theuse of the wrench, to tighten a given element beyond a predeterminedtorque for the socket 9 will automatically be released as soon as thatpredetermined torque is exceeded.

After the toggle T has cammed over, the wrench is immediately ready forre-use on the next element to be tightened, by merely turning the wrenchover and applying the other end of the socket 9 to the element to betightened. The toggle need not be returned to its original position andthe wrench will operate equally as ethciently from either side. Thus asubstantial saving in time is efiected in addition to the positiveprevention of damage to the element to be tightened.

The torque required to cause the toggle T to cam over may bepredetermined at various degrees of compression exerted on the spring 25and the same may be indicated on the shank i3 by graduating the shank asindicated in Fig. 3. Thus the user may readily adjust the compressionexerted on the spring 35 by tightening or loosening the portion of thehandle carrying the set screw with respect to the shank l8. When thehandle has been adjusted so that the desired torque will be required tocause the toggle T to cam over, that fact will be indicated and the userwill be appraised thereof through reference to the reading hole 28 asshown in Fig. 2. Thus it is possible to adjust the wrench readily to camover at various predetermined torques.

It should be noted that my wrench is also adjustable to compensate forchanges which may take place over a period of time in the resistancewhich the spring 25 offers to compression. By adjusting the nut 33 onthe thread end of the rod 31, the amount of compression can be changedeven though the two sections of the handle remain in the same positionwith respect to each other.

Thus it can be seen that I have provided a torque wrench constructed toautomatically release when the torque exerted thereon is such as toexceed a predetermined torque. This positively prevents the elementbeing tightened by the wrench from being damaged. It is highly importantin aircraft assembling operations and in the expanding of ferrules thatexact predetermined torques be exerted on the element to be rotated. Mywrench provides a ready and efilcient means for accomplishing thisfunction.

It should be noted that in addition to the fact that my wrenchautomatically releases itself when the torque applied thereto exceeds apredetermined amount, it is also reversible in nature so that no time islost in its use when moving from one element which has just beentightened to the next element to be tightened, It should also be notedthat my wrench is .capable of ready adjustment to various predeterminedtorques.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the parts withoutdeparting from the scope of my invention.

What I hereby claim is:

1. An automatically releasing torque wrench comprising an at leastpartially hollow head member, a rotatable body mounted for free rotationin said head member and adapted to engagingly receive the element to beturned by the wrench, said body having engagement means on itscircumferential surface, a handle secured to said head member and havinga central bore, a rod mounted within said bore for limited. slidingmovement longitudinally of the handle, resilient means constantly urgingsaid rod toward said rotatable body, and toggle mechanism connected tothe outer end of said rod and normally extending diagonally with respectthereto and adapted to cooperate with said engaging means to engage saidrotatable body, said toggle mechanism, being swingably mounted on saidrod and disposed with respect to said head member to permit the togglemechanism to swing to the opposite side of the longitudinal center ofsaid rod sufficiently far to permit the same, when a sufficiently strongtorque is exerted on said rotatable body, to force said rod inwardlydespite said resilient means, to disengage said rotatable body to permitthe latter to thereafter turn freely in the direction of that torquewithout being re-engaged by said toggle mechanism.

2. An automatically releasing torque wrench comprising an at leastpartially hollow head member, a rotatable body mounted for free rotationin said head member and adapted to engagingly receive the element to beturned by the wrench, said body having a recess formed in itscircumferential surface, a handle secured to said head member and havinga central longitudinal bore, a rod mounted within the bore of saidhandle for limited sliding movement longitudinally of the handle,resilient means constantly urging said rod outwardly from said handleand toward said rotatable body, and toggle means connected to the outerend of said rod and normally extending diagonally with respect theretoand engaging said rotatable body within said recess, said toggle means,when a sufficiently strong torque is exerted on said rotatable body toforce said rod inwardly despite said resilient means, being swingablymounted and disposed to permit the same to move to the opposite side ofthe longitudinal center of said rod sumciently far to permit the same todisengage the recess of said rotatable body to permit the latter tothereafter turn freely in the direction or" that torque without beingre-engaged by said toggle mechanism.

3. An automatically releasing torque wrench comprising an at leastpartially hollow head member, a rotatable body mounted for free rotationin the hollow portion of said head member and adapted to engaginglyreceive the element to be turned by the wrench, a handle member rigidlysecured to said head member and having a central longitudinallyextending bore adjacent to and communicating with said hollow portion ofsaid head member, a rod mounted within said bore for limited slidingmovement longitudinally of the handle, the outer end of said rodextending into said hollow portion of said head member,

resilient means adjacent the inner end of said rod constantly urgingsaid rod toward said rotatable body, toggle mechanism swingably mountedon the outer end of said rod and having an engaging element on the outerend portion of the same, the outer circumferential surface of saidrotatable body being adapted to cooperate with said engagement elementto permit releasable interconnection between said rotatable body andsaid toggle mechanism, said toggle mechanism being spaced sufficientlyfar from the walls of said head member defining said hollow portion topermit the same to be swung sufficiently far to either side of thelongitudinal center of said rod to disengage said engaging element fromsaid rotatable body, and resilient means adjacent tne outer end of saidrod constantly urging said engaging element into engaging relation withrespect to said rotatable body, said toggle mechanism being normallydisposed diagonally with respect to said rod and functioning to swing tothe opposite side of the longi tudinal center of said red when asuihciently strong torque is applied to said body to cause said rod tomove away from said body to thereafter permit said body to turn freelyin the direction of that torque and thereafter remaining in engag ingposition with respect to said rotatable body to engage the same in theevent the direction of the torque is reverse i. [in automaticallyreleasing torque wrench comprising an at least partially hollow headieniher, a rotatable body mounted for free rotation in the hollow prtion of said head member and adapted to engagingly receive the elementto be turned by the wrench, said body having a re cess formed in itsouter circumferential extending substantially parallel to the rotationof said body, a handle ri idly secui ed to said head member and having acentral longitudinal bore communicating a hollow portion of said headmember, a mounted hin r longitudinally of the handle, the outer endportion of said rod extending into i of said head member, relativelystrong s ring carried with n said bore and constantly i 'ng said rodoutwardly toward rotatable body with a predetermined force, a togglemember adapted to be engage,

in said recess of said body wardly extending shoulder thereon, arelatively weak spring carried by the outer end portion or said rod andarranged to constantly abut against said shoulder and urge toggle membertoward longitudinal alignment with said rod where mod in by said keyelement is constantly contact with said rotatable bO' gle member beingnormally disposed diagon 1y ith respect to said rod and being spacedsuiiiciently 1-' far from the walls of said head member defining saidhollow portion to permit the same to swing sufficiently far to eitherside of the longitudinal center of said rod to disengage said keyelement from said recess whereby after a suiiiciently strong torque hasbeen exerted on said rotatable body to force said rod inwardly and. tocause said toggle member to swing over to the opposite side of thelongitudinal center of said rod, it becomes impossible to tighten anelement beyond such a predetermined torque.

5. An automatically releasing torque wrench comprising a handle having acentral longitudinal bore, extending inwardly from its outer end, a headmember rigidly secured to the outer end portion of said handle andhaving an opening formed therethrough extending transversely to saidhandle and communicating with said bore, an open ended socket mountedfor rotation within said opening on the longitudinal axis of the openingand adapted to engagingly receive in either of its ends the element tobe turned, a rod mounted with said bore for limited sliding movementlongitudinally of the handle and extending into said opening to a pointadjacent said socket, a spring element carried within said bore andengaging the inner end portion of said rod and constantly urging thesame toward said socket, a toggle member swingably mounted on the outerend portion of said rod in a plane substantially parallel to the planeof rotation of said socket, said toggle member having a key element onits outer end, and normally extending diagonally with respect to saidrod, said socket having a recess formed in its outer circumferentialsurface to receive said key element in engaging relation, and means forresiliently urging said toggle member toward longitudinal alignment withsaid rod whereby said key element will be maintainec i abutting relationwith respect to said socket, said spring element being under apredetermined copression whereby when a predetermined torque is exertedon said socket said rod may be forced inwardly despite said springelement and whereby said toggle ember may swing over to the oppositeside of the longitudinal centeror" said rod to thereafter permit saidsocket to turn relatively freely in the direction of that torque andthereby prevent the element being turned by the wrench from beingtightened excessively and thereby simultaneously becoming adapted forinstant use for tightening a similar element by merely turning thewrench over, said toggle member being spaced suiliciently far from thewalls defining said opening to permit the same to swing to either sideor the longitudinal center of the rod sufiiciently far to cause said keyelement to be dis-en'- gaged from said recess.

6. An automatically releasing torque wrench comprising an at leastpartially hollow head member, a rotatable body mounted for free rotationin the hollow portion of said head member and adapted to engaginglyreceive the element to be turned by the wrench, a handle member rigidlysecured to said head member and having a central longitudinallyextending bore adjacent to and communicating with said hollow portion ofsaid head member, a rod mounted within said bore for limited slidingmovement longitudinally of the handle, the outer end of said rodextending into said hollow portion of said head member, resilient meansadjacent the inner end of said rod constantly urging said rod towardsaid rotatable body, toggle mechanism swingably mounted on the outer endof said rod and having an engaging element on the outer end portion ofthe same, the outer circumferential surface of said rotatable body beingadap-tecl to cooperate with said engagement element to permit releasableinterconnection between said rotatable body and said toggle mechanism,said toggle mechanism being spaced sufficiently far from the walls ofsaid head member defining said hollow portion to permit the same to beswung sufficiently far to either side of the longitudinal center of saidrod to disengage said, engaging element from said rotatable body, andresilient means adjacent the outer end of said rod constantly urgingsaid engaging element into engagin relation with respect to saidrotatable body, said toggle mechanism being normally disposed diagonallywith respect to said rod, said first mentioned resilient means being ofsubstantially greater strength than said second mentioned resilientmeans whereby when a sufficiently strong torque is exerted on saidrotatable body to force said rod inwardly despite said resilient means,said toggle mechanism will swing to the opposite side of thelongitudinal center of said rod to thereafter permit said rotatable bodyto turn relatively freely in the direction of that torque and willremain in engaging position with respect to said rotatable body toengage the same in the event the direction of the torque is reversed.

7. An automatically releasing torque wrench comprising a head member, arotatable body mounted for free rotation on said head member and adaptedto be connected to the element to be turned by the wrench, a handlemember rigidly secured to said head member and having a centrallongitudinally extending bore, a rod mounted within said bore forlimited sliding movement longitudinally of the handle and extending to apoint adjacent said rotatable body, resilient means constantly urgingsaid rod toward said rotatable body, toggle mechanism swingably mountedon the outer end of said rod and hating an engaging element on the outerend portion of the same, a portion of said rotatable body being adaptedto cooperate with said engagement element to permit releasibleinterconnection between said rotatable body and said toggle mechanism,said toggle mechanism being free to swing sufficiently far to eitherside of the longitudinal center of said rod to disengage said engagingelement from said rotatable body, and resilient means adjacent the outerend of said rod constantly urging said engaging element into engagingrelation with respect to rotatable body and toward alignment with saidrod and being weaker than said first mentioned resilient means, saidtoggle mechanism being normally disposed diagonally with respect to saidrod, and functioning when a sufficiently strong torque is exerted onsaid rotatable body to force said rod inwardly despit said resilientmeans, to swing to the opposite side of the longitudinal center of saidrod permitting said rotatable body to turn freely in the direction ofthat torque and at the same time remaining in engaging position withrespect to said rotatable body to engage the same in the event thedirection of the torque is reversed.

OREN B. HARMES.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,303,595 Rifilard May 13, 1919 2,179,855 Latimer Nov. 14,1939 2,332,971 Johnson Oct. 26, 1943 2,556,587 Keen June 12, 1951FOREIGN PATENTS Number Country Date 109,874 Australia Feb. 20, 1940774,185 France Sept. 17, 1934

